"B: The Beginning" is a 12-episode anime series set in the fictional archipelago of Cremona, where advanced technology and crime intertwine. The story unfolds through two parallel narratives that eventually converge. The first centers on Keith Kazama Flick, a brilliant but enigmatic investigator for the Royal Investigation Service (RIS), who is tasked with solving a series of gruesome murders linked to a mysterious criminal organization known as "Market Maker." Keith possesses exceptional deductive skills and a tragic past tied to the organization, which drives his relentless pursuit of justice.

The second narrative follows Koku, a young man with supernatural abilities, including enhanced strength, speed, and the power to manifest wings. Koku is searching for his lost love, Yuna, whose disappearance is connected to the same criminal underworld Keith is investigating. Koku’s abilities stem from a secretive genetic experiment conducted by Market Maker, which also ties him to Keith’s past. As the series progresses, it becomes clear that Koku and Keith share a deeper connection, rooted in their mutual history with the organization.

The plot intensifies as Market Maker’s true motives are revealed: they aim to create a new world order by manipulating human evolution through genetic engineering. The organization’s leader, Minatsuki, is a former scientist who believes in transcending humanity’s limitations, even if it means sacrificing countless lives. Keith and Koku, along with their allies—including Lily Hoshina, a determined RIS officer, and Eric Toga, a skilled hacker—must confront Market Maker’s forces to prevent their catastrophic plans.

The series blends elements of crime thriller, science fiction, and supernatural action, with a focus on intricate character relationships and moral dilemmas. Themes of identity, sacrifice, and the consequences of unchecked ambition are explored as the characters navigate a world where the line between humanity and monstrosity is increasingly blurred. The narrative’s dual focus on Keith’s detective work and Koku’s personal quest creates a dynamic interplay between mystery and emotional depth, culminating in a climactic confrontation that resolves the immediate threat while leaving room for future developments.